Abstract: Objective To investigate the anti-recombinant human granulocyte-macrophage colony-stimulating factor (anti-rhGM-CSF) antibody formation and neutralizing antibody activity of rhGM-CSF suppository in repeated-dose toxicity studies in rats and Beagle dogs. Methods The rats received vaginal suppository of rhGM-CSF at doses of 0 (placebo), 0.24, 0.96 and 3.84 mg/kg and Beagle dogs at a dose of 0 (placebo), 0.07, 0.28 and 1.12 mg/kg (daily dosing for up to 3 months), respectively. The titer of anti-rhGM-CSF antibody in serum was measured using indirect enzyme-linked immunosorbent assay (ELISA) and the neutralizing antibodies were determined by an in vitro bioassay. Results Antibodies to rhGM-CSF were detected in all the rats treated with rhGM-CSF suppository during the treatment and recovery period, and neutralizing antibodies were found in serum samples which developed binding antibodies. No anti-rhGM-CSF antibodies were observed in dogs during the experiment of all groups. Conclusion The rats serum contained rhGM-CSF binding antibodies which neutralized the biological activity of rhGM-CSF. Antibodies to rhGM-CSF were not detected in the Beagle dogs serum.

Key words: recombinant human granulocyte-macrophage colony-stimulating factor suppository, immunogenicity, rats, Beagle dogs